Project II will study the binding of general anesthetics to designed cavities in a model protein, a designed 4-alpha-helix bundle, and will interpret the results with the aid of interaction parameters derived from gas-liquid partition studies. The central problem in this project is to obtain structures of the designed protein with and without the bound ligand. This project has two aims. The first aim is to obtain interaction parameters describing the physics of interaction between groups in a general anesthetic and groups in organic liquids classes to resemble various classes of amino acid side chains in proteins. Specific aim 2 proposes to use a scaffold formed from a designed 4-alpha-helix bundle protein containing a cavity designed to contain a general anesthetic (GA) such as halothane, measure the structure and dynamics of the protein with and without the bound anesthetic, and measure the binding constant and stoichiometry of the GA-scaffold interaction. The aim is to use the results to test the knowledge gained in the first aim to find out if it is adequate to predict, or at least interpret, the properties of a GA-protein cavity interaction and also to explore how binding of a GA to a protein cavity may affect the structure and dynamics of the protein.